Acquire a lock on two mutexes and avoid deadlock

Question

The following code contains a potential deadlock, but seems to be necessary: to safely copy data to one container from another, both containers must be locked to prevent cha

Answer 1

As @Mellester mentioned you can use std::lock for locking multiple mutexes avoiding deadlock.

#include 

void foo::copy(const foo& rhs)
{
    std::lock(pMutex, rhs.pMutex);

    std::lock_guard l1(pMutex, std::adopt_lock);
    std::lock_guard l2(rhs.pMutex, std::adopt_lock);

    // do copy
}

But note to check that rhs is not a *this since in this case std::lock will lead to UB due to locking same mutex.